The electrofluidic device is driven based on the change of the interface between polar fluid and non-polar fluid by applying electric field thereon.
FIGS. 1A-1B are drawings, schematically illustrating the driving mechanism of the conventional electrofluidic device. In FIG. 1A, the polar fluid 104 and non-polar fluid 106 are filled between two transparent substrate 100a, 100b and form an interface 108. Polar fluid 104 can be water containing pigment or colorant for an example. The non-polar fluid 106 can be transparent oil for an example. The hydrophobic layers 102a, 102b are disposed on the two substrates 100a, 100b in contact with the polar fluid 104 and the non-polar fluid to form a convex-shape polar fluid. An electrode layer 103 is further disposed between the substrate 100a and the hydrophobic layer 102a. A the state without applying operation voltages, the polar fluid 104 is converged due to the surface tension at the hydrophobic layers.
In FIG. 1B, when the polar fluid 104 is treated as the ground terminal and the electrode layer 103 is applied with a voltage 110, the interface 108 is changed as a slant due to the effect of electric field, and the polar fluid 104 is driven to shifting toward the left. The area covered by the polar fluid 104 displays the colors, which is the color of pigment or colorant carried by the polar fluid.
Based on the foregoing mechanism, it can be used to design the display device. FIGS. 2A-2B are cross-sectional views, schematically illustrating a conventional structure of electrofluidic device. In FIG. 2A, an insulating layer 122 is disposed a transparent substrate 120a. The insulating layer 122 has a groove 124. A hydrophobic layer 126 is disposed on the insulating layer 122. An electrode layer 127 and a hydrophobic layer 128 are disposed on another substrate 120b. The electrode layer 127 is transparent conductive material, such as indium tin oxide (ITO). The polar fluid 104 is disposed in the groove 124 and between the hydrophobic layers 126 and 128. The non-polar fluid 106 is disposed between the hydrophobic layers 126 and 128 and form a balancing interface with the non-polar fluid 104, such as water, which can be dyed with pigment or colorant. The non-polar fluid 106 is transparent fluid, such as oil. When no voltage is applied, due to the effect of surface tension at the hydrophobic layer, the polar fluid 104 is converged in the groove 124. The substrate is also transparent. When the light enters, the light maintains the original color, such as white, of the light, and transmits the substrates 120a, 120b, the electrode layer 127 and the transparent non-polar fluid 106.
In FIG. 2B, when the polar fluid 104 is treated as the ground and the electrode layer is applied with a positive voltage, the polar fluid 104 is driven out from the groove 124 and shifted outward to the area other than the groove 124. Since the polar fluid 104 has the pigment or colorant, the transmitting light through the polar fluid 104 appears the color of the pigment or colorant. When the voltage stops, due to the effect between the polar fluid 104 and the hydrophobic layer, the polar fluid 104 is pulled back to the groove 124.
The conventional electrofluidic display panel is composed of multiple electrofluidic devices, which are arranged in an array form. FIGS. 3A-3B are drawing, schematically illustrating the operation mechanism of the electrofluidic display panel. In FIG. 3A, each pixel has the polar fluid disposed in the groove and the peripheral region of the groove is filled with the non-polar fluid. The periphery of the pixel has the duct 130. The duct 130 is also filled with the non-polar fluid and can isolate the operation of each pixel when the polar fluid is driven. When there is no operation voltage applied, the polar fluid 134 remains in the groove. In FIG. 3B, when the operation voltage is applied, the polar fluid 134 is pulled out from the groove and extends to cover the whole pixel area. Since the polar fluid is dyed with pigment or colorant, the color displaying effect can be achieved. The duct 130 can avoid the interference between the polar fluids in different pixels when operation is performed.